It's an useful standard for a JS only web app. Once you work a bit with React/Angular/Aurelia, you start noticing that having your styles somewhere in a styles

It's an useful standard for a JS only web app. Once you work a bit with React/Angular/Aurelia, you start noticing that having your styles somewhere in a stylesheet is somewhat clumsy for reusable components or overly dynamic components. You end up having to refactor with your stylesheets very often as your app grows and things can quickly turn into a mess. You are then tempted to put style="" declaration in your .jshtml (or equivalent) templates but that's a also mess. So your start developing a way to inject styles into dom elements. This then grow up into some strange frankeinstein that no other devs can work with because you documented nothing... so you simply start using https://www.styled-components.com https://www.styled-components.com instead.